ANTARCTIC BRYOZOA — ROGICK 273 



Hippopleurifera apparently may have either a pleurocyst or a 

 tremocyst (Osbiirii, 1952, pi, 35, fig. 7; pi. 36, fig. 1; and Hastings, 

 1949, pi. 12). Two Umbonula species may have a median process 

 which might pass for a Ijn-ula. Umbonula arctica (Sars) 1850 has a 

 median process of a size varying from a point (Osburn, 1952, pl. 36, 

 fig. 6) to a sizable toothlike mucro (Robertson, 1908, pl. 23, fig. 78). 

 Umbonula dentata (Waters) 1904 is midway between these two ex- 

 tremes, having a delicate, bifid, incurving denticle simulating a lyrula 

 or mucro. In view of the above deviations it is believed the family 

 should be characterized as follows. 



Diagnosis: Frontal a tremocyst or pleurocyst. Pleurocyst some- 

 times forms areolae, costulae, and a prominent umbo. Umbo oc- 

 casionally directed orally, like a median denticle. Orifice large, sub- 

 orbicular to subquadi-angular. Peristome poorly developed or absent. 

 Avicularia either single, median and below, or lateral or about, with 

 respect to the orifice. Ovicell hyperstomial and usually perforated. 



Brown (1952, pp. 288-289) does not recognize the family Umbo- 

 nulidae but includes Umbonula with Escharoides and Exochella in the 

 family Exochellidae. 



The taxonomic status of the Umbonulidae should be more carefully 

 studied, particularly in its relationship to the Petraliidae, Exochellidae, 

 and Smittinidae, because it is not yet clearly defined and because some 

 of its species intergrade with the other families. Incidentally, for 

 many years Umbonula has been classed with the Smittinidae. 



Genus Umbonula Hincks, 1880 



Umbonella Hincks, 1880, pp. 316-317, text. 



Umbonula Hincks, 1880, atlas, pl. 39 (Hincks used the name Umbonella in the 



text, then discovered it was preoccupied and corrected it in the atlas). — 



Canu and Bassler, 1920, p. 494.— Hastings, 1944, pp. 273-284; 1949a, pp. 



205-211.— Lagaaij, 1952, p. 90.— Brown, 1952, pp. 288-289, 304-308.— 



Bassler, 1953, p. G196. 



The above synonymy refers to significant papers only. 



Remarks: Hincks' original description of the genus is as follows: 

 "... primary orifice suborbicular or sub quadrangular, lower margin 

 slightly curved inwards, peristome not elevated, no secondary orifice; 

 a prominent umbo (? avicularian cell) immediately below the mouth, 

 supporting an avicularium . . . encrusting." 



To this Canu and Bassler formally add "frontal is a pleurocyst -with 

 costules surrounded by areolae . . . 20-30 tentacles . . . neither lyrula 

 nor cardelles." To this Brown (p. 305) adds "ovicells with radiating 

 pores or finely perforate." Lastly, Lagaaij adds "Avicularia paired, 

 lateral to the orifice, or single, embedded in the distal slope of the 

 umbo." 



